The societal risk exposure for the off-site population was assessed using an “F-N curve” and the “indicative societal risk criteria” described in HIPAP4 [2]. The “F-N curve” for the Project is presented in Figure 9, which also shows the “indicative societal risk criteria”.
Figure 9: Societal Risk Results – Off-site Population
As can be seen from Figure 9, the “F-N curve” lies below the “negligible” line. In this region, the societal risk is not considered significant, provided other individual risk criteria are met. As described in the preceding sections, the individual risk criteria for fatality and injury are satisfied and therefore the societal risk is also considered tolerable.
10.4 RISK OF PROPERTY DAMAGE AND ACCIDENT PROPAGATION
The risk of property damage and accident propagation was assessed using the impairment criteria defined in Section 6.4. The resulting risk contour for heat radiation is presented in Figure 10. A corresponding risk contour for explosion overpressure is not presented because the explosion event frequency is below the criterion level.
1.00E-09 1.00E-08 1.00E-07 1.00E-06 1.00E-05 1.00E-04 1.00E-03 1.00E-02 1.00E-01 1 10 100 1000 F re q u e n c y o f N o r m o re f a ta li ti e s ( F , /y e a r) Number of Fatalities (N)
Intolerable
Negligible
ALARP
Figure 10: Location-Specific Risk of Property Damage and Accident Propagation – Heat Radiation (50 x 10-6per year)
The tolerability of results was determined by comparison with the following risk criteria defined within HIPAP4 [2]:
Incident heat flux radiation at neighbouring potentially hazardous installations or at land zoned to accommodate such installations should not exceed a risk of 50 x 10-6per year for the 23 kW/m2heat flux level.
Incident explosion overpressure at neighbouring potentially hazardous installations, at land zoned to accommodate such installations or at nearest public buildings should not exceed a risk of 50 x 10-6per year for the 14 kPa explosion overpressure level.
The 50 x 10-6per year risk contour for heat flux radiation is contained on-site. Therefore, it does not reach neighbouring areas, including potentially hazardous installations. This aspect of the criteria is satisfied.
In Figure 10, the 50 x 10-6per year risk contour appears as numerous individual sections of the same contours that are limited to the immediate area. For example, within the Tank Farm, different sections of the contours are contained within the corresponding bunded area. This demonstrates that these contours do not extend to impact surrounding infrastructure, such as storage tanks within adjoining areas.
The risk of explosion at the facility did not exceed 50 x 10-6per year. Consequently, a risk plot for explosion overpressure is not presented, as the risk does not exceed the criteria level of 50 x 10-6per year at any location. This aspect of the criteria is therefore satisfied.
The acceptability of the risk criteria is summarised in Table 1.
Table 13: Risk of Property Damage And Accident Propagation Tolerance Criteria [2]
Risk Criteria
Tolerance Criteria (risk in a million per
year)
Tolerability
Incident heat flux radiation at neighbouring potentially hazardous installations or at
land zoned to accommodate such
installations for the 23 kW/m2heat flux.
50
The relevant LSIR contours do not extend to these areas. The criteria are
met.
Incident explosion overpressure at
neighbouring potentially hazardous
installations, at land zoned to
accommodate such installations or at nearest public buildings for the 14 kPa explosion overpressure level
50
10.5 BIOPHYSICAL RISK
The risk to the biophysical environment examines the potential effects on the long-term viability of the ecosystem or any species within it. The risk was assessed by examining release scenarios associated with the operations of the facility. In assessing the potential impact, the analysis considered the controls that would prevent, or mitigate, the impact an incident could have on the surrounding environment.
For the wharf, the QRA identified release scenarios at the product loading arms and the pipelines along the wharf. A release from this equipment could affect the marine environment of Botany Bay. However, there are a number of controls in place that would minimise the potential for a release. The equipment items are subject to testing and inspection programs, in line with Caltex’ integrity management programs. During unloading operations, there are personnel in attendance who, if a release occurred, would be able to detect the leak and isolate the source. Additionally, a spill at the loading arms would be contained within the purpose-built spill containment areas. These factors will limit the amount of material that would typically be released following a failure. A release of product at the wharf is not considered likely to threaten the long-term viability of the ecosystem.
For the tank farm, the QRA identified release scenarios at the product storage tanks, as well as the associated pipelines and pumps. The potential for release from this equipment is managed by Caltex through a maintenance program to ensure the integrity of equipment. If a release occurs, it would be contained within the bunded areas surrounding storage tanks and pumps or within the pipeways.
detection within the Terminal that includes routine operator surveillance, routine “dead tank” monitoring and flammable vapour detection. An appropriate response would then be activated to clean-up a spill. Additionally, the containment areas can be drained to the oily water system, where product would be retained, preventing the discharge of any remaining product direct to the environment. Therefore, a release of product within the terminal would not threaten the long-term viability of the ecosystem.
Caltex also maintains an Environmental Aspects and Impacts Register, as part of its requirements for compliance with ISO 14001 [22]. The register identifies potential sources of accidental release, assesses the potential consequence, identifies key risk controls and ranks the risk using Caltex’s Riskman2 process.